SYNTHESIS AND SEPARATION OF A DIASTEREOMERIC PAIR OF PHOSPHONOPEPTIDE INHIBITORS OF THE CYCLIC-AMP-DEPENDENT PROTEIN-KINASE CATALYTIC SUBUNIT

In this paper we report the establishment of a novel procedure to synthesize a nonhydrolyzable phosphonopeptide dead-end inhibitor of the catalytic subunit of cAMP-dependent protein kinase. This procedure has been optimized to maximize the peptide yield and gives a diastereomeric pair of heptapeptides that can be separated on a C-18 reverse phase HPLC column. The two peptides have been characterized by NMR and the ability of these peptides to inhibit the reaction of the catalytic subunit of cAMP-dependent protein kinase. Peptide A has a dissociation constant of 9 micromolar, and is a 10-fold better inhibitor as compared to peptide B. On the basis of this 10-fold greater inhibition afforded by peptide A, this peptide is assigned the all L-form configuration. It is expected that this procedure can easily be adapted to synthesize a variety of different peptide inhibitors which involve a nonhydrolyzable phosphate on an amino acid.